﻿using System;
using System.Net;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Linq.Expressions;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;

namespace LINQAmazonProvider
{
        //The actual "query" actually is an expression that represents the query as a tree of LINQ query operators/method calls.
        //the purpose of this class is to traverse this tree and search for local variable definitions and convert them to 
        //an object that can be used with reflection.
        public abstract class ExpressionVisitor
        {

            protected ExpressionVisitor()
            {

            }



            protected virtual Expression Visit(Expression exp){
                if (exp == null)

                    return exp;

                switch (exp.NodeType)
                {
                    case ExpressionType.Quote:
                    case ExpressionType.Not:
                        return this.VisitUnary((UnaryExpression)exp);

                    case ExpressionType.And:
                    case ExpressionType.AndAlso:
                    case ExpressionType.Or:
                    case ExpressionType.OrElse:
                    case ExpressionType.LessThan:
                    case ExpressionType.LessThanOrEqual:
                    case ExpressionType.GreaterThan:
                    case ExpressionType.GreaterThanOrEqual:
                    case ExpressionType.Equal:
                    case ExpressionType.NotEqual:
                        return this.VisitBinary((BinaryExpression)exp);

                    case ExpressionType.TypeIs:
                        return this.VisitTypeIs((TypeBinaryExpression)exp);

                    case ExpressionType.Conditional:
                        return this.VisitConditional((ConditionalExpression)exp);

                    case ExpressionType.Constant:

                        return this.VisitConstant((ConstantExpression)exp);

                    case ExpressionType.Parameter:

                        return this.VisitParameter((ParameterExpression)exp);

                    case ExpressionType.MemberAccess:
                        return this.VisitMemberAccess((MemberExpression)exp);

                    case ExpressionType.Call:
                        return this.VisitMethodCall((MethodCallExpression)exp);

                    case ExpressionType.Lambda:
                        return this.VisitLambda((LambdaExpression)exp);

                    case ExpressionType.New:
                        return this.VisitNew((NewExpression)exp);

                    default:
                        throw new Exception(string.Format("Unhandled expression type: '{0}'", exp.NodeType));
                }
            }



            protected virtual MemberBinding VisitBinding(MemberBinding binding)
            {

                switch (binding.BindingType)
                {

                    case MemberBindingType.Assignment:

                        return this.VisitMemberAssignment((MemberAssignment)binding);

                    case MemberBindingType.MemberBinding:

                        return this.VisitMemberMemberBinding((MemberMemberBinding)binding);

                    case MemberBindingType.ListBinding:

                        return this.VisitMemberListBinding((MemberListBinding)binding);

                    default:

                        throw new Exception(string.Format("Unhandled binding type '{0}'", binding.BindingType));

                }

            }



            protected virtual ElementInit VisitElementInitializer(ElementInit initializer)
            {

                ReadOnlyCollection<Expression> arguments = this.VisitExpressionList(initializer.Arguments);

                if (arguments != initializer.Arguments)
                {

                    return Expression.ElementInit(initializer.AddMethod, arguments);

                }

                return initializer;

            }



            protected virtual Expression VisitUnary(UnaryExpression u)
            {

                Expression operand = this.Visit(u.Operand);

                if (operand != u.Operand)
                {

                    return Expression.MakeUnary(u.NodeType, operand, u.Type, u.Method);

                }

                return u;

            }



            protected virtual Expression VisitBinary(BinaryExpression b)
            {

                Expression left = this.Visit(b.Left);

                Expression right = this.Visit(b.Right);

                Expression conversion = this.Visit(b.Conversion);

                if (left != b.Left || right != b.Right || conversion != b.Conversion)
                {

                    if (b.NodeType == ExpressionType.Coalesce && b.Conversion != null)

                        return Expression.Coalesce(left, right, conversion as LambdaExpression);

                    else

                        return Expression.MakeBinary(b.NodeType, left, right, b.IsLiftedToNull, b.Method);

                }

                return b;

            }



            protected virtual Expression VisitTypeIs(TypeBinaryExpression b)
            {

                Expression expr = this.Visit(b.Expression);

                if (expr != b.Expression)
                {

                    return Expression.TypeIs(expr, b.TypeOperand);

                }

                return b;

            }



            protected virtual Expression VisitConstant(ConstantExpression c)
            {

                return c;

            }



            protected virtual Expression VisitConditional(ConditionalExpression c)
            {

                Expression test = this.Visit(c.Test);

                Expression ifTrue = this.Visit(c.IfTrue);

                Expression ifFalse = this.Visit(c.IfFalse);

                if (test != c.Test || ifTrue != c.IfTrue || ifFalse != c.IfFalse)
                {

                    return Expression.Condition(test, ifTrue, ifFalse);

                }

                return c;

            }



            protected virtual Expression VisitParameter(ParameterExpression p)
            {

                return p;

            }



            protected virtual Expression VisitMemberAccess(MemberExpression m)
            {

                Expression exp = this.Visit(m.Expression);

                if (exp != m.Expression)
                {

                    return Expression.MakeMemberAccess(exp, m.Member);

                }

                return m;

            }



            protected virtual Expression VisitMethodCall(MethodCallExpression m)
            {

                Expression obj = this.Visit(m.Object);

                IEnumerable<Expression> args = this.VisitExpressionList(m.Arguments);

                if (obj != m.Object || args != m.Arguments)
                {

                    return Expression.Call(obj, m.Method, args);

                }

                return m;

            }



            protected virtual ReadOnlyCollection<Expression> VisitExpressionList(ReadOnlyCollection<Expression> original)
            {

                List<Expression> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    Expression p = this.Visit(original[i]);

                    if (list != null)
                    {

                        list.Add(p);

                    }

                    else if (p != original[i])
                    {

                        list = new List<Expression>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(p);

                    }

                }

                if (list != null)
                {

                    return list.AsReadOnly();

                }

                return original;

            }



            protected virtual MemberAssignment VisitMemberAssignment(MemberAssignment assignment)
            {

                Expression e = this.Visit(assignment.Expression);

                if (e != assignment.Expression)
                {

                    return Expression.Bind(assignment.Member, e);

                }

                return assignment;

            }



            protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding binding)
            {

                IEnumerable<MemberBinding> bindings = this.VisitBindingList(binding.Bindings);

                if (bindings != binding.Bindings)
                {

                    return Expression.MemberBind(binding.Member, bindings);

                }

                return binding;

            }



            protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding)
            {

                IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(binding.Initializers);

                if (initializers != binding.Initializers)
                {

                    return Expression.ListBind(binding.Member, initializers);

                }

                return binding;

            }



            protected virtual IEnumerable<MemberBinding> VisitBindingList(ReadOnlyCollection<MemberBinding> original)
            {

                List<MemberBinding> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    MemberBinding b = this.VisitBinding(original[i]);

                    if (list != null)
                    {

                        list.Add(b);

                    }

                    else if (b != original[i])
                    {

                        list = new List<MemberBinding>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(b);

                    }

                }

                if (list != null)

                    return list;

                return original;

            }



            protected virtual IEnumerable<ElementInit> VisitElementInitializerList(ReadOnlyCollection<ElementInit> original)
            {

                List<ElementInit> list = null;

                for (int i = 0, n = original.Count; i < n; i++)
                {

                    ElementInit init = this.VisitElementInitializer(original[i]);

                    if (list != null)
                    {

                        list.Add(init);

                    }

                    else if (init != original[i])
                    {

                        list = new List<ElementInit>(n);

                        for (int j = 0; j < i; j++)
                        {

                            list.Add(original[j]);

                        }

                        list.Add(init);

                    }

                }

                if (list != null)

                    return list;

                return original;

            }



            protected virtual Expression VisitLambda(LambdaExpression lambda)
            {

                Expression body = this.Visit(lambda.Body);

                if (body != lambda.Body)
                {

                    return Expression.Lambda(lambda.Type, body, lambda.Parameters);

                }

                return lambda;

            }



            protected virtual NewExpression VisitNew(NewExpression nex)
            {

                IEnumerable<Expression> args = this.VisitExpressionList(nex.Arguments);

                if (args != nex.Arguments)
                {

                    if (nex.Members != null)

                        return Expression.New(nex.Constructor, args, nex.Members);

                    else

                        return Expression.New(nex.Constructor, args);

                }

                return nex;

            }



            protected virtual Expression VisitMemberInit(MemberInitExpression init)
            {

                NewExpression n = this.VisitNew(init.NewExpression);

                IEnumerable<MemberBinding> bindings = this.VisitBindingList(init.Bindings);

                if (n != init.NewExpression || bindings != init.Bindings)
                {

                    return Expression.MemberInit(n, bindings);

                }

                return init;

            }



            protected virtual Expression VisitListInit(ListInitExpression init)
            {

                NewExpression n = this.VisitNew(init.NewExpression);

                IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(init.Initializers);

                if (n != init.NewExpression || initializers != init.Initializers)
                {

                    return Expression.ListInit(n, initializers);

                }

                return init;

            }



            protected virtual Expression VisitNewArray(NewArrayExpression na)
            {

                IEnumerable<Expression> exprs = this.VisitExpressionList(na.Expressions);

                if (exprs != na.Expressions)
                {

                    if (na.NodeType == ExpressionType.NewArrayInit)
                    {

                        return Expression.NewArrayInit(na.Type.GetElementType(), exprs);

                    }

                    else
                    {

                        return Expression.NewArrayBounds(na.Type.GetElementType(), exprs);

                    }

                }

                return na;

            }



            protected virtual Expression VisitInvocation(InvocationExpression iv)
            {

                IEnumerable<Expression> args = this.VisitExpressionList(iv.Arguments);

                Expression expr = this.Visit(iv.Expression);

                if (args != iv.Arguments || expr != iv.Expression)
                {

                    return Expression.Invoke(expr, args);

                }

                return iv;

            }

        }
    }
